1. Field of the Invention
The present invention relates generally to a cleaning device, cleaning system, treating device and cleaning method for removing deposits adhering to the surface of a semiconductor wafer or the like.
2. Description of Related Background Art
In general, in order to form a semiconductor integrated circuit or the like, various treatments, such as thin-film deposition on a semiconductor wafer, oxidation, diffusion and etching, are repeatedly carried out. In this case, for example, before the above described treatments are carried out, a cleaning treatment for removing organic substances, metal impurities, particles, natural oxide films and so forth, which adhere to the surface of a wafer, is carried out if necessary. In addition, although resist masks, side-wall protection layers for enhancing anisotropy and so forth are used when oxide films and so forth are etched in order to form wiring patterns and holes, these resist masks and so forth are also removed by a cleaning treatment or some treatment in the subsequent process. For example, when a desired wiring pattern is formed on a semiconductor wafer in this etching process, a resist 4 is first applied on the top face of an interlayer dielectric film 2 of, e.g., SiO2, as a film of a semiconductor wafer to be etched, and this is patterned by a typical exposure technique to form a mask 6, as shown in FIG. 10(A). Furthermore, reference number 8 denotes a metal wiring layer of, e.g., copper or aluminum.
Then, as shown in FIG. 10(B), the resist mask 6 is used as a mask to scrape the interlayer dielectric film 2 by means of the dry etching using plasma or the like, to expose the metal wiring layer 8 underlying the interlayer dielectric film 2 to form a desired pattern. In this case, in order to prevent the broadening of etching in lateral directions to enhance anisotropy of the etching, a side-wall protection layer 10, which is produced by the reaction of etching gas, the shavings of the interlayer dielectric film 2 or the resists peeled off by the etching, is positively formed on the side walls of the interlayer dielectric film 2 with the progress of the etching.
The etching treatment is thus completed, O2 is then introduced to ash and remove the undesired resist mask 6 by the plasma ashing treatment as shown in FIG. 10(C). Thereafter, the side-wall protection layer is also removed by the wet cleaning or the like.
By the way, the above described wet cleaning is carried out generally by completely immersing a plurality of semiconductor wafers, which are objects to be treated, in a storage tank filled with a cleaning solution, such as a chemical, at a time, or as shown in FIG. 11, by clamping a semiconductor wafer W on a turntable 12 to supply a cleaning solution 16, such as a chemical or a rinsing fluid (e.g., ultrapure water), in the form of liquid or spray from a nozzle 14 while rotating the turntable 12, to diffuse the cleaning solution 16 on the surface of the wafer W by centrifugal force. In addition, drying is also carried out while the wafer W is rotating.
By the way, in the above described cleaning device, there are some cases where the wafer is exposed to atmosphere during cleaning to oxidize the metal wiring layer and so forth on the surface thereof or to oxidize the metal wiring layer by oxygen and so forth mixed in the cleaning solution. In addition, in the above described method for immersing the wafer in the storage tank, there are some cases where the flow velocity of the cleaning fluid on the surface of the wafer is very low, so that cleaning can not sufficiently carried out.
In addition, when the cleaning solution is supplied to the central portion of the rotating wafer, the angular velocity increases from the central portion of the wafer to the peripheral portion thereof, so that the velocity distribution is ununiform. Therefore, there are some cases where the cleaning and drying of the central portion of a low angular velocity are insufficient, so that the inplane uniformity of the cleaning and drying treatments is damaged. In particular, when the temperature control for the chemical is severe, there is a problem in that the temperature of the chemical decreases toward the peripheral portion of the wafer.
In addition, in the case of the above described system for rotating the turntable 12, it is required to provide a rotating mechanism, so that the size of the system increases. As a result, it is difficult to stack a plurality of stages of such large systems, so that the systems must be flatted. Therefore, there is a problem in that the foot print increases when the number of cleaning treatment parts increases.
Moreover, when the metal film 8 having the structure shown in FIG. 10 is a copper film formed by the Cu metal damascene technique, there is a problem in that the copper film is oxidized during the O2 plasma ashing, so that its electric characteristics deteriorate. Therefore, it is strongly desired to provide a cleaning method or cleaning device capable of rapidly removing the resist mask 6 and the side-wall protection layer 10 without the need of the O2 plasma ashing.
In addition, since the treating atmosphere is not closed in the conventional immersion type and spin type cleaning systems, there is a problem in that the composition of the cleaning liquid is varied by vaporization of volatile constituents in the cleaning fluid and the metal wiring layer, particularly the copper wiring layer, is oxidized due to oxygen in the atmosphere in the treating chamber.
It is therefore an object of the present invention to eliminate the aforementioned problems and to provide a cleaning device, cleaning system and cleaning method capable of preventing a metal wiring layer or the like of an object to be treated, from being oxidized.
It is another object of the present invention to provide a cleaning device, cleaning system and cleaning method capable of rapidly and efficiently carrying out cleaning by using a cleaning fluid having a high flow velocity.
In order to accomplish the aforementioned and other objects, according to one aspect of the present invention, a cleaning device comprises: a cleaning container, in which a treating space for housing an object to be treated is formed; a fluid storage tank for storing a cleaning fluid for treating the object; a supply line for supplying the cleaning fluid from the fluid storage tank to the cleaning container; and a reflux line for returning the cleaning fluid from the cleaning container to the fluid storage tank, wherein the cleaning container, the fluid storage tank, the supply line and the reflux line are associated with each other for forming a closed cleaning fluid circulating line, and wherein a cross-sectional area of the treating space perpendicular to a direction from the supply line to the reflux line is predetermined times as large as the maximum value of the cross sectional area of the object perpendicular to the direction.
According to this device, when the cleaning fluid is allowed to flow through the cleaning container to clean the surface of the object to be treated, it is possible to rapidly and efficiently carry out the cleaning treatment without exposing the cleaning fluid to outside air. In addition, since air does not enter the treating container, it is possible to prevent a cleaned metal wiring layer, such as a copper film, from being oxidized. In other words, it is possible to efficiently use the cleaning fluid by circulating the cleaning fluid, and it is possible to prevent the cleaning fluid from being deteriorated due to oxidation and vaporization since the cleaning fluid is used in the closed state without contacting air.
The cleaning device may further comprise a recovering fluid supply system for supplying a recovering fluid to the cleaning container without exposing the recovering fluid to outside air, to recover the cleaning fluid in the fluid storage tank. Thus, it is possible to efficiently use the cleaning fluid.
The cleaning device may further comprise: a rinsing fluid supply system for supplying a rinsing fluid to the cleaning container without exposing the rinsing fluid to outside air; a dry fluid supply system for supplying a dry fluid to the cleaning container without exposing the dry fluid to outside air; and supply control means for controlling so as to selectively continuously supply one of the fluids to the cleaning container every kind of the fluids. Thus, it is possible to continuously carry out the rinsing and drying of the object in the same device.
The cleaning device may further comprise a second fluid storage tank for storing a residual liquid treating cleaning fluid for treating a residual liquid remaining in the cleaning fluid circulating line, and wherein a closed residual liquid treating/circulating line for allowing the residual liquid treating cleaning fluid to flow through the cleaning fluid circulating line without exposing the residual liquid treating cleaning fluid to outside air, to recover the residual liquid treating cleaning fluid in the second fluid storage tank is formed. Thus, it is possible to prevent the presence of the residual liquid remaining in the piping at the last step from having the influence on the next step even if the cleaning fluid circulating line is formed as a circulating line.
The fluid storage tank may comprise a plurality of storage tanks for storing cleaning fluids corresponding to a plurality of kinds of deposits, respectively, which adhere to the surface of the object to be treated. Thus, cleaning fluids having different functions can be supplied into the cleaning device without being mixed with each other to continuously carry out treatments, e.g., to continuously clean and remove a resist mask and side-wall protection layer on the surface of a semiconductor wafer after plasma etching.
The object may be a plate, and the cleaning device may further comprise fluid guiding means for allowing the cleaning fluid to flow in parallel to the surface of the plate. Thus, it is possible to allow the cleaning fluid to flow to uniformly carry out the treatment.
If the cleaning device has turbulent flow forming means for promoting a turbulent flow in the cleaning fluid, it is possible to reduce the influence of an immobile layer, which is produced on the surface of the object due to the viscosity of the chemical by the turbulent flow, to rapidly and efficiently carry out the cleaning treatment.
The turbulent flow forming means may comprise a sound wave radiating unit for irradiating the surface of the object with sound waves.
The sound wave radiating unit may comprise an ultrasonic element for producing ultrasonic waves, and a buffer tank for efficiently propagating the ultrasonic waves produced by the ultrasonic element.
The turbulent flow forming means may comprise an irregular portion provided on an inner wall surface of the cleaning container.
A plurality of cleaning devices, each of which is the same as the above described cleaning device, may be arranged in one of vertical, lateral and longitudinal directions. Thus, it is possible to reduce the occupied floor area to greatly reduce the foot print.
According to another aspect of the present invention, a treating device comprises: a transfer chamber capable of being maintained air-tightly; a load-lock chamber which is air-tightly connected to the transfer chamber for introducing/discharging an object to be treated, into/from the outside; at least one vacuum treating chamber which is air-tightly connected to the transfer chamber via a transfer port; a cleaning chamber which is air-tightly connected to the transfer chamber via a transfer port; transfer means, provided in the transfer chamber, for transferring the object between the load-lock chamber, the vacuum treating chamber and the cleaning device, the cleaning device comprising: a cleaning container, in which a treating space having a volume predetermined times as large as that of an object to be treated is formed; a fluid storage tank for storing a cleaning fluid for treating the object; a supply line for supplying the cleaning fluid from the fluid storage tank to the cleaning container; and a reflux line for returning the cleaning fluid from the cleaning container to the fluid storage tank, wherein the cleaning container, the fluid storage tank, the supply line and the reflux line are associated with each other for forming a closed cleaning fluid circulating line. If the cleaning device having the closed cleaning fluid circulating line is combined with the vacuum treating device and so forth in the form of a cluster, it is possible to carry out a series of consistent treating steps including a cleaning step without exposing the wafer W to outside air.
According to a further aspect of the present invention, there is provided a cleaning method wherein a cleaning fluid is supplied from a fluid storage tank for housing therein the cleaning fluid, to a cleaning container having a treating space having a cross-sectional area perpendicular to a direction of a laminar flow of a fluid crossing on said object that is predetermined times as large as the maximum value of the cross-sectional area of an object to be treated perpendicular to said direction, and the cleaning fluid is returned to the fluid storage tank to circulate the cleaning fluid without being exposed to outside air. In this method, the cleaning fluid may comprise a resist removing liquid for removing a resist mask, which is patterned on the surface of the object, and the object, and a side-wall protection side-wall protection layer removing liquids for removing a side-wall protection layer adhering to a side wall of an etched layer when dry-etching the object using the resist mask as a mask, and the resist removing liquid may be supplied to treat the object after the side-wall protection layer removing liquid is supplied to treat the object.
According to this method, it is possible to rapidly and simply remove both of the side-wall protection layer and the resist mask, which adhere to the surface of the wafer, by continuous wet cleaning treatments. In addition, by carrying out the cleaning treatment in this order, it is possible to avoid the hardening of the side-wall protection layer, which can occur when the treatments are carried out in the opposite order, and unexpected accidents, such as the covering of the side-wall protection layer with the hardening layer which can be formed on the surface of the resist mask.